diff --git a/contrib/postgres_fdw/connection.c b/contrib/postgres_fdw/connection.c
index 8a8d3b4481..52e262cc18 100644
--- a/contrib/postgres_fdw/connection.c
+++ b/contrib/postgres_fdw/connection.c
@@ -822,6 +822,9 @@ do_sql_command_end(PGconn *conn, const char *sql, bool consume_input)
* those scans. A disadvantage is that we can't provide sane emulation of
* READ COMMITTED behavior --- it would be nice if we had some other way to
* control which remote queries share a snapshot.
+ *
+ * Note that we always start remote transactions with the same read/write
+ * and deferrable properties as the local (top-level) transaction.
*/
static void
begin_remote_xact(ConnCacheEntry *entry)
@@ -831,17 +834,23 @@ begin_remote_xact(ConnCacheEntry *entry)
/* Start main transaction if we haven't yet */
if (entry->xact_depth <= 0)
{
- const char *sql;
+ StringInfoData sql;
elog(DEBUG3, "starting remote transaction on connection %p",
entry->conn);
+ initStringInfo(&sql);
+ appendStringInfoString(&sql, "START TRANSACTION ISOLATION LEVEL ");
if (IsolationIsSerializable())
- sql = "START TRANSACTION ISOLATION LEVEL SERIALIZABLE";
+ appendStringInfoString(&sql, "SERIALIZABLE");
else
- sql = "START TRANSACTION ISOLATION LEVEL REPEATABLE READ";
+ appendStringInfoString(&sql, "REPEATABLE READ");
+ if (TopTransactionIsReadOnly())
+ appendStringInfoString(&sql, " READ ONLY");
+ if (XactDeferrable)
+ appendStringInfoString(&sql, " DEFERRABLE");
entry->changing_xact_state = true;
- do_sql_command(entry->conn, sql);
+ do_sql_command(entry->conn, sql.data);
entry->xact_depth = 1;
entry->changing_xact_state = false;
}
diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 8447b289cb..ba3bb7665a 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -12263,6 +12263,78 @@ SELECT count(*) FROM remote_application_name
DROP FOREIGN TABLE remote_application_name;
DROP VIEW my_application_name;
-- ===================================================================
+-- test read-only and/or deferrable transactions
+-- ===================================================================
+CREATE TABLE loct (f1 int, f2 text);
+CREATE FUNCTION locf() RETURNS SETOF loct LANGUAGE SQL AS
+ 'UPDATE public.loct SET f2 = f2 || f2 RETURNING *';
+CREATE VIEW locv AS SELECT t.* FROM locf() t;
+CREATE FOREIGN TABLE remt (f1 int, f2 text)
+ SERVER loopback OPTIONS (table_name 'locv');
+INSERT INTO loct VALUES (1, 'foo'), (2, 'bar');
+SELECT * FROM loct;
+ f1 | f2
+----+-----
+ 1 | foo
+ 2 | bar
+(2 rows)
+
+SELECT * FROM remt; -- should work
+ f1 | f2
+----+--------
+ 1 | foofoo
+ 2 | barbar
+(2 rows)
+
+SELECT * FROM loct;
+ f1 | f2
+----+--------
+ 1 | foofoo
+ 2 | barbar
+(2 rows)
+
+START TRANSACTION READ ONLY;
+SELECT * FROM remt; -- should fail
+ERROR: cannot execute UPDATE in a read-only transaction
+CONTEXT: SQL function "locf" statement 1
+remote SQL command: SELECT f1, f2 FROM public.locv
+ROLLBACK;
+DROP FOREIGN TABLE remt;
+CREATE FOREIGN TABLE remt (f1 int, f2 text)
+ SERVER loopback OPTIONS (table_name 'loct');
+START TRANSACTION ISOLATION LEVEL SERIALIZABLE READ ONLY;
+SELECT * FROM remt;
+ f1 | f2
+----+--------
+ 1 | foofoo
+ 2 | barbar
+(2 rows)
+
+COMMIT;
+START TRANSACTION ISOLATION LEVEL SERIALIZABLE DEFERRABLE;
+SELECT * FROM remt;
+ f1 | f2
+----+--------
+ 1 | foofoo
+ 2 | barbar
+(2 rows)
+
+COMMIT;
+START TRANSACTION ISOLATION LEVEL SERIALIZABLE READ ONLY DEFERRABLE;
+SELECT * FROM remt;
+ f1 | f2
+----+--------
+ 1 | foofoo
+ 2 | barbar
+(2 rows)
+
+COMMIT;
+-- Clean up
+DROP FOREIGN TABLE remt;
+DROP VIEW locv;
+DROP FUNCTION locf();
+DROP TABLE loct;
+-- ===================================================================
-- test parallel commit and parallel abort
-- ===================================================================
ALTER SERVER loopback OPTIONS (ADD parallel_commit 'true');
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index 1598d9e086..292281981c 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -4165,6 +4165,48 @@ SELECT count(*) FROM remote_application_name
DROP FOREIGN TABLE remote_application_name;
DROP VIEW my_application_name;
+-- ===================================================================
+-- test read-only and/or deferrable transactions
+-- ===================================================================
+CREATE TABLE loct (f1 int, f2 text);
+CREATE FUNCTION locf() RETURNS SETOF loct LANGUAGE SQL AS
+ 'UPDATE public.loct SET f2 = f2 || f2 RETURNING *';
+CREATE VIEW locv AS SELECT t.* FROM locf() t;
+CREATE FOREIGN TABLE remt (f1 int, f2 text)
+ SERVER loopback OPTIONS (table_name 'locv');
+
+INSERT INTO loct VALUES (1, 'foo'), (2, 'bar');
+SELECT * FROM loct;
+
+SELECT * FROM remt; -- should work
+SELECT * FROM loct;
+
+START TRANSACTION READ ONLY;
+SELECT * FROM remt; -- should fail
+ROLLBACK;
+
+DROP FOREIGN TABLE remt;
+CREATE FOREIGN TABLE remt (f1 int, f2 text)
+ SERVER loopback OPTIONS (table_name 'loct');
+
+START TRANSACTION ISOLATION LEVEL SERIALIZABLE READ ONLY;
+SELECT * FROM remt;
+COMMIT;
+
+START TRANSACTION ISOLATION LEVEL SERIALIZABLE DEFERRABLE;
+SELECT * FROM remt;
+COMMIT;
+
+START TRANSACTION ISOLATION LEVEL SERIALIZABLE READ ONLY DEFERRABLE;
+SELECT * FROM remt;
+COMMIT;
+
+-- Clean up
+DROP FOREIGN TABLE remt;
+DROP VIEW locv;
+DROP FUNCTION locf();
+DROP TABLE loct;
+
-- ===================================================================
-- test parallel commit and parallel abort
-- ===================================================================
diff --git a/doc/src/sgml/postgres-fdw.sgml b/doc/src/sgml/postgres-fdw.sgml
index d2998c13d5..13d1944ab5 100644
--- a/doc/src/sgml/postgres-fdw.sgml
+++ b/doc/src/sgml/postgres-fdw.sgml
@@ -1071,6 +1071,22 @@ postgres=# SELECT postgres_fdw_disconnect_all();
PostgreSQL release might modify these rules.
+
+ The remote transaction is opened in the same read/write mode as the local
+ transaction: if the local transaction has been declared
+ READ ONLY at the top level, the remote transaction is
+ opened in READ ONLY mode, otherwise it is opened in
+ READ WRITE mode.
+
+
+
+ The remote transaction is also opened in the same deferrable mode as the
+ local transaction: if the local transaction has been declared
+ DEFERRABLE at the top level, the remote transaction is
+ opened in DEFERRABLE mode, otherwise it is opened in
+ NOT DEFERRABLE mode.
+
+
Note that it is currently not supported by
postgres_fdw to prepare the remote transaction for
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 1b4f21a88d..3e79922c8f 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -1043,6 +1043,27 @@ TransactionStartedDuringRecovery(void)
return CurrentTransactionState->startedInRecovery;
}
+/*
+ * TopTransactionIsReadOnly
+ *
+ * Returns true if the transaction has been declared READ ONLY at the top
+ * level.
+ */
+bool
+TopTransactionIsReadOnly(void)
+{
+ TransactionState s = CurrentTransactionState;
+
+ if (s->nestingLevel == 1)
+ return XactReadOnly;
+ while (s->nestingLevel > 2)
+ {
+ Assert(s->parent != NULL);
+ s = s->parent;
+ }
+ return s->prevXactReadOnly;
+}
+
/*
* EnterParallelMode
*/
diff --git a/src/include/access/xact.h b/src/include/access/xact.h
index b2bc10ee04..0160eb1d91 100644
--- a/src/include/access/xact.h
+++ b/src/include/access/xact.h
@@ -458,6 +458,7 @@ extern TimestampTz GetCurrentTransactionStopTimestamp(void);
extern void SetCurrentStatementStartTimestamp(void);
extern int GetCurrentTransactionNestLevel(void);
extern bool TransactionIdIsCurrentTransactionId(TransactionId xid);
+extern bool TopTransactionIsReadOnly(void);
extern void CommandCounterIncrement(void);
extern void ForceSyncCommit(void);
extern void StartTransactionCommand(void);